How long does it take for an A record to propagate? I was under the impression that changes to an A record would propagate much quicker than updating your name servers.
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migrated from stackoverflow.com Mar 23 '10 at 13:38
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There is no one answer to what you're asking. It all depends on your configuration of TTL values and the particular ISPs that might be caching results that your end-users will be using. Recursive DNS servers (the kind at your ISP that are used by clients to resolve names of Internet resources) cache the results of lookups. The caching is supposed to be based on a Time To Live (TTL) value specified by the DNS server that is authoritative for the record. It's good practice to specify a TTL value short enough to accomodate day-to-day changes that you might need to make, but long enough so that there's some "win" in caching. It's a "win" for everybody because it reduces the load on authoritative DNS servers, and reduces everybody's bandwidth utilization. If you set your TTLs very low you'll increase load and bandwidth utilization on your authoritative DNS servers. If you set your TTLs very high you'll be unable to make changes to your records that will "take effect" quickly. It's a balancing act. Some ISPs are brain-damaged and ignore the TTL values specified by the authoritative DNS servers and substitute their own. There's nothing you can do about this, other than complaining to those ISPs and hoping that they cave to social pressure. This particular type of abuse isn't a technical problem. If everybody "plays by the rules" you can make a change to a given record "take effect" very quickly. You would perform an exponential backoff of the TTL value leading up to the time you'll make the change (1 day, 12 hours, 6 hours, 3 hours, etc... down to however small you'd like to go), make the change, and then bring the TTL back up to your desired value. Usually, though, somebody doesn't respect your TTL and you're forced to continue answering on the old IP address, name, etc, for some period of time until the brain-damaged TTL-ignoring DNS server operators sort themselves out. Personally, I've seen changes "take effect" immediately, in a few hours, and in some cases with a particular brain-damaged ISP, after several days. Doing a backoff of your TTL and being mindful of how the process works will increase your changes for success, but you can't ever be sure what some well-meaning idiot might be doing with their DNS servers... | |||
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As Andrew said, caching. It depends on the TTL you set, and it also depends if the cache servers respect the TTL. Generally you can expect a change to propagate to take from few hours to 1 day. | |||
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You can do a "ipconfig /registerdns" on your system to get the latest changes. | |||
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